为何grep -I/--binary-files=without-match仍匹配特定二进制文件？

我有一个16位压缩格式的二进制文件：

# file /tmp/43174744S.0601.Z
/tmp/43174744S.0601.Z: compress'd data 16 bits

grep可正常识别它为二进制文件：

# grep "" /tmp/43174744S.0601.Z
Binary file /tmp/43174744S.0601.Z matches

但尝试用-I或--binary-files=without-match选项排除二进制文件时，该文件仍会被匹配：

# grep -I "" /tmp/43174744S.0601.Z
Binary file /tmp/43174744S.0601.Z matches
# grep --binary-files=without-match "" /tmp/43174744S.0601.Z
Binary file /tmp/43174744S.0601.Z matches
# grep -Il "" /tmp/43174744S.0601.Z
/tmp/43174744S.0601.Z

这是否属于bug？因为这些选项对其他二进制文件（如.so库）有效：

# grep -I "" /usr/lib/*.so
# grep "" /usr/lib/*.so
Binary file /usr/lib/klibc-abS-oVB3xeRN8SFypUWbQvR33nc.so matches
Binary file /usr/lib/libdmmp.so matches
Binary file /usr/lib/libmpathcmd.so matches
Binary file /usr/lib/libmpathpersist.so matches
Binary file /usr/lib/libmultipath.so matches

测试涉及的grep版本为grep (GNU grep) 2.16和grep (GNU grep) 3.4。

更新1 #

提取该文件前2字节生成新文件后，问题依旧存在：

# head -c2 /tmp/43174744S.0601.Z > /tmp/43174744S.0601.C2.Z
# cat /tmp/43174744S.0601.C2.Z | od -a
0000000  us  gs
0000002
# grep -I "" /tmp/43174744S.0601.C2.Z
Binary file /tmp/43174744S.0601.C2.Z matches

更新2 #

新建内容看似相同的文件后，grep表现正常：

# echo -n $'\37'$'\35' > /tmp/test
# cat /tmp/test | od -a
0000000  us  gs
0000002
# cat /tmp/43174744S.0601.C2.Z | od -a
0000000  us  gs
0000002
# grep "" /tmp/43174744S.0601.C2.Z
Binary file /tmp/43174744S.0601.C2.Z matches
# grep "" /tmp/test

#

但执行cp /tmp/43174744S.0601.C2.Z /tmp/test后，问题再次出现，说明问题与原文件本身相关。

更新3 #

提供两个文件的十六进制dump输出：

# hexdump -C /tmp/43174744S.0601.C2.Z
00000000  1f 9d                                             |..|
00000002

# hexdump -C /tmp/test
00000000  1f 1d                                             |..|
00000002

内容的提问来源于stack exchange，提问作者mgutt